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Martin Spoustafor the ATLAS Collaboration
Charles UniversityPrague
26th international conference on ultrarelativistic heavy-ion collisions,February 5-11, 2017, Chicago
Inclusive jets and jet substructure
in 2.76 TeV and 5.02 TeV pp and Pb+Pb collisionswith the ATLAS detector
Quark Matter 2017, February 5-11, 2017 2
Introduction
Measurements of inclusive jet suppression:
– Phys. Lett. B 719 (2013) 220
– Phys. Rev. Lett. 114 (2015) 072302
– ATLAS-CONF-2017-009 … new for QMMeasurements of internal structure of jets:
– Phys. Lett. B739 (2014) 320
– arXiv:1702.00674 … new for QM
– ATLAS-CONF-2017-005 … new for QMUsed data:
– Run 1: Pb+Pb: √sNN = 2.76 TeV, Lint = 0.14 nb-1
pp: √s = 2.76 TeV, Lint = 4.2 pb-1
– Run 2: Pb+Pb: √sNN = 5.02 TeV, Lint = 0.49 nb-1
pp: √s = 5.02 TeV, Lint = 25 pb-1
Quark Matter 2017, February 5-11, 2017 3
Inclusive jet suppression
Jet yield in heavy ion collisions
Jet cross-section in pp collisions
Nuclear tickness fuction
Nuclear modification factor quantifies the magnitude of the jet suppression which is dominantly due to final state interactions with constituents of the medium
Number of expected jets per event of a given centrality
Quark Matter 2017, February 5-11, 2017 4
Jet reconstruction performance in run 2
Realistic jet simulations: NLO POWHEG+PYTHIA8 MC + minimum bias Pb+Pb data overlay.
Good understanding of jet energy scale.
Expected behavior of jet energy resolution.
Jet energy scale Jet energy resolution
Quark Matter 2017, February 5-11, 2017 5
Jet reconstruction performance in run 2
… Example of the improvement in the jet energy scale: implementing the higher order flow corrections.
=> Jet energy scale does not dependent on the orientation with respect to the reaction plane. See also poster
by Akshat Puri
Quark Matter 2017, February 5-11, 2017 6
Jet cross-section in pp collisions5.02 TeV2.76 TeV
Quark Matter 2017, February 5-11, 2017 7
Jet yeilds in Pb+Pb collisions
5.02 TeV2.76 TeV
Quark Matter 2017, February 5-11, 2017 8
A modest grow of jet RAA with increasing jet pT.
Still significant suppression even for 60-80% centrality bin.
Jet RAA: pT-dependence,
PRL 114 (2015) 072302√sNN = 2.76 TeV
Quark Matter 2017, February 5-11, 2017 9
Quantifying jet RAA in the pT range of 100 GeV to 1 TeV and for |y|<2.8.
Allows for detailed comparison with predictions e.g.: X-N Wang et al. (arXiv:1611.07211), Chien and Vitev (arXiv:1509.07257), Casalderrey-Solana et al. (arXiv:1508.00815).
Jet RAA: pT-dependence,√sNN = 5.02 TeV
ATLAS-CONF-2017-009
Quark Matter 2017, February 5-11, 2017 10
Jet RAA: pT-dependence,2.76 TeV versus 5.02 TeV
Same magnitude of RAA within systematic uncertainties seen at the two different center-of-mass energies.
Significant reduction of (experimental) systematic uncertainties in the new measurement mainly due to taking the data in the same running period.
ATLAS-CONF-2017-009
Quark Matter 2017, February 5-11, 2017 11
Jet RAA: y-dependence,√sNN = 2.76 TeV
… no rapidity dependence seen
PRL 114 (2015) 072302
Quark Matter 2017, February 5-11, 2017 12
Jet RAA: y-dependence,√sNN = 5.02 TeV
jet
pT
Vertical-axis: ratio of RAA in a given rapidity to the RAA for jets with|y|<0.3.
With increasing jet pT RAA getting smaller in the forward region as compared to the mid-rapidity region(predicted in arXiv:1504.05169).
ATLAS-CONF-2017-009
Quark Matter 2017, February 5-11, 2017 13
Jet RAA: Npart-dependence√sNN = 5.02 TeV
… smooth decrease of RAA with increasing centrality
ATLAS-CONF-2017-009
Quark Matter 2017, February 5-11, 2017 14
Internal structure of jets at 2.76 TeV
rapidity of jet
cen
tral
ity
z
arXiv:1702.00674
See also talk by Radim Slovák
Tue 11:40
Quark Matter 2017, February 5-11, 2017 15
Internal structure of jets at 2.76 TeV
rapidity of jet
cen
tral
ity
arXiv:1702.00674
Centrality dependenceEnhancement at low z and at high z
Suppression at intermediate z
Rapidity dependence… next slide
Jet pt dependenceNo significant dependence on jet pT
(not shown here)
Quark Matter 2017, February 5-11, 2017 16
Internal structure of jets at 2.76 TeV
Sign of a larger enhancement at high z in the mid-rapidity region as compared to the forward rapidity region (explanation for this proposed in arXiv:1504.05169).
arXiv:1702.00674
Quark Matter 2017, February 5-11, 2017 17
Internal structure of jetsin pp
Fragmentation functions and distributions of charge particle momentum inside jet measured in pp collisions both at 2.76 TeV and 5.02 TeV.
=> Can be used as a realistic pp reference for jet quenching studies and to tune the MC generators.
ATLAS-CONF-2017-005
Quark Matter 2017, February 5-11, 2017 18
Internal structure of jets at 5.02 TeV
Ratios of D(z) distributions for tracks with pT>4 GeV.
Same features seen in 5.02 TeV as in 2.76 TeV (the enhancement at high z and depletion at intermediate z).
ATLAS-CONF-2017-005
Quark Matter 2017, February 5-11, 2017 19
Internal structure of jets at 5.02 TeV
… 5.02 TeV measurementagrees with 2.76 TeVmeasurement at thecomparable z domain
See also talk by Radim Slovák
Tue 11:40
ATLAS-CONF-2017-005
Quark Matter 2017, February 5-11, 2017 20
Charged hadron RAA
Charged hadron RAA measured for pT=1-300 GeV
–> a trend of flattening at high pT
See also poster by Alexander
Milov
ATLAS-CONF-2017-012
Quark Matter 2017, February 5-11, 2017 21
Charged hadron RAA
versus jet RAA
Quark Matter 2017, February 5-11, 2017 22
Summary
Inclusive jet suppression:
– Significant suppression seen up to ~1 TeV.
– Rapidity dependence of RAA observed for high-pT jets.
– Quantitatively consistent RAA between 2.76 TeV and 5.02 TeV.
Internal structure of jets:
– Measured differentially in jet pT and rapidity.
– Enhancement at low z, suppression at intermediate z, and enhancement at high z precisely quantified.
– Different size of high-z enhancement seen for forward and mid-rapidity jets.
– Qualitatively same modifications of jet fragmentation seen at 2.76 TeV and 5.02 TeV.
Quark Matter 2017, February 5-11, 2017 23
Backup slides
Quark Matter 2017, February 5-11, 2017 24
Jet energy scale uncertainties
Detailed estimation of jet energy scale uncertainty.Using in situ techniques (γ+jet and Z+jet) and limits on the impact of modified fragmentation on jet energy scale.
Same level of rigor as in precision pQCD measurement should be a standard for precision HI measurements in the run II.
Quark Matter 2017, February 5-11, 2017 25
Run 2 jet yields and Raa uncertainties
Quark Matter 2017, February 5-11, 2017 26
Jet RAA
Quark Matter 2017, February 5-11, 2017 27
Jet RAA
Quark Matter 2017, February 5-11, 2017 28
Internal structure of jets at 5.02 TeV
… no jet pT dependence observed
ATLAS-CONF-2017-005
Quark Matter 2017, February 5-11, 2017 29
RD(z)
in Pb+Pb for R=0.4 jets
Quark Matter 2017, February 5-11, 2017 30
RD(pt)
in Pb+Pb for R=0.4 jets
A clear evolution with centrality